*{
    margin: 0;
    padding: 0;
}

.qingchu{
    /* 兼容IE低版本的hack写法 */
    zoom: 1;
}
.qingchu::before{
    content: '';
    display: table;
    clear: both;
}
.qingchu::after{
    content: '';
    /* 必写 */
    display: table;
    clear: both;
    visibility: hidden;
    width: 0;
    line-height: 0;
}